Under the Great Seal of the Realm, she signed an elaborate notice of approval which proclaimed, in transcribed calligraphy, consent to the union of 'Our Most Dearly Beloved Grandson Prince William Arthur Philip Louis of Wales, K.G. and Our Trusty and Well-beloved Catherine Elizabeth Middleton'.

Tied to the bottom of the approval by gold braiding is a large red wax Great Seal of the Realm.

William had to ask his grandmother's consent to marry because of a law dating from the 18th century.

Under the Royal Marriages Act 1772, all descendants of George II must obtain the sovereign's agreement before they wed, otherwise the marriage is invalid.

The 'Instrument of Consent' features decorative artwork chosen by the artist to represent the groom and bride-to-be.

There is a gold cipher of the couple's entwined initials beneath the prince's coronet, but St James's Palace said this was not the couple's official symbol.

A white lily represents St Catherine of Siena, whose feast day falls on April 29th and with whom Miss Middleton shares her name.

Beneath it is a Welsh leek surrounded by William's white three-pronged second in line to the throne label and a tiny red escallop from the Spencer family Arms.

There is also a red dragon - the heraldic symbol of Wales, the UK's floral emblems - the rose, thistle and shamrock - and the Garter belt, William's blue and gold Order of the Garter belt, as well as a large gold E for Elizabeth.

The Queen's signature 'Elizabeth R' can be seen at the top right of the Instrument of Consent, which is dated 'the ninth day of February Two Thousand and Eleven in the Sixtieth year of Our Reign'.

It was signed 'by the Queen herself, signed with her own hand' at a Privy Council meeting after the monarch made a formal Declaration of Consent.

It reads: 'NOW KNOW YE that We have consented and do by these Presents signify Our Consent to the contracting of Matrimony between Our Most Dearly Beloved Grandson Prince William Arthur Philip Louis of Wales K.G. and Our Trusty and Well-beloved Catherine Elizabeth Middleton.'